Photographic process and composition



Silvzr Halide S+ru+um May 16, 1961 M. M. MORSE 7 2,984,565

' PHOTOGRAPHIC PROCESS AND cowosmon Filed March 18, 1960 Silver HalideDeveloper "N and Solvcn'f, and Cys+eine Silver Recepi'ive Shahim ifAqueous So|u+ion of Supporl' FIG. I

Silv cr Tr unsfer Reversal Prin+ Con'laining Cys+eine }v\/ I /A .4Suppori -22 ATTORNEYS United States Patent PHOTOGRAPHIC PROCESS ANDCOMPOSITION Meme M. Morse, Boston, Mass asslgnor to PolaroidCorporation, Cambridge, Mass, a corporation of Delawere Filed Mar. 18,1960, Ser. No. 16,100

7 Claim. (Cl. 96-29) The present invention relates to photography and,more particularly, to the production of photographic prints by silvertransfer.

Silver transfer techniques generally involve subjecting a silver halidelatent image to developing and dissolving reagents in the presence of asilver-receptive environment where a visible silver print is formed. Forexample, a fluid, such as an alkaline aqueous solution of a silverhalide developing agent and a silver solvent, is applied to a pair ofstrata, for example a photoexposed silver halide stratum and asilver-receptive stratum that are superposed. Thereafter, the strata aremaintained in superposed relation for a predetermined processing periodduring which the reagents develop exposed silver halide to silver andreact with unreduced silver halide to form a soluble silver complex thatis reduced to silver in the print-receptive stratum to form a positiveprint. The present invention contemplates improving silver transfertechniques with the aid of an additive, initially disposed, for example,either in the fluid or on one of the sheets, that serves to enhance thecharacter of the resulting print.

The primary object of the present invention is to enhance the blacknessof a silver transfer print with the aid of cysteine, otherwise known asalpha-amino-betathiol-propionic acid.

Other objects of the invention will in part be obvious and will in partappear hereinafter.

The invention accordingly comprises the process involving the severalsteps and the relation and order of one or more of such steps withrespect to each of the others and the composition possessing thefeatures, prop erties and the relation of components which areexemplified in the following detailed disclosure, and the scope of theapplication of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention,reference should be had to the following detailed description taken inconnection with the accompanying drawing wherein:

Figure 1 is an exaggerated cross-sectional view of photographicmaterials undergoing a preferred process embodying the presentinvention; and

Fig. 2 is an exaggerated cross-sectional view of the print produced bythe process of Fig. 1.

Generally, Fig. 1 shows a silver halide processing fluid 10 spread in auniformly thin layer between the adjacent superposed surfaces of asilver halide photosensitive sheet 12 and a silver print-receptive sheet14. Such spreading, for example, is accomplished by advancing thesheets, to-. gether with the fluid, between a pair of pressure-applyingrollers. Preferably, the liquid is sufficiently viscous to be readilycontrolled as it is spread, in accordance with the teachings of US.Patent No. 2,543,181, issued to Edwin H. Land on February 27, 1951. Inaccordance cysteine, represented by the formula:

0 IYTH:

H0--("J-CHCH:8H

in viscous alkaline solution with a silver halide developing agent suchas hydroquinone, a silver halide solvent such as sodium thiosulfate anda thickener such as a watersoluble polymer or gum or an insolubleemulsifiable oil. The cysteine is present in a concentration elfectiveto render the resulting silver transfer image substantially more neutralin tone, e.g., blue-black, as compared with the image which would beobtained in its absence. In a preferred embodiment, the cysteine ispresent in a concentration, by weight of said solution, of about 0.001to 0.60%. The photosensitive sheet includes a gelatino silver halidestratum 16 on a suitable support 18 and the print-receptive sheetincludes a silver-receptive stratum 20 on a suitable support 22. Withina predetermined period after solution 10 is spread, the reagents thereinform a negative'print in silver halide stratum 16 by-reducing silverhalide to silver and react with unreduced silver halide to form a silvercomplex which difiuses into the layer of processing fluid tosilver-receptive stratum 20 where it is reduced to silver to form apositive print. The presence of the cysteine is responsible for aconsiderably more neutral tone in the resulting print than would existin its absence.

' Example Grams Hydroquinone 52.0 Sodium thiosulfate 14.5 Cysteine 5.2Sodium hydroxide 54.6 Sodium sulfite 78.0 Sodium carboxymethyl cellulose93.0 Water 1860.0

Here, silver halide stratum 16 and silver-receptive stratum 20 aremaintained in superposed relation with processing fluid 10 therebetweenfor a period of approximately from 40 to 120 seconds in duration. At theend of this period, silver-receptive stratum 20 and layer of solution 10are stripped from silver halide stratum 16 to display a positive printof substantially richer and blacker tone than would have been obtainedin the absence of cysteine. The presence of cysteine also appreciablyincreases the effective speed of the process.

The proportions of the ingredients of processing fluid 10 may be variedwithin wide limits. However, where the processing period is asspecified, within the range of from 40 to 120 seconds in accordance withthe now conventional duration of silver diffusion transfer processingperiods, practical results are achieved where, by total weight of thefluid, 'the developing agent ranges from 1 to 8%, the silver halidesolvent from 0.3 to 10%, and the thickener is in suflicientconcentration. to impart to the fluid a viscosity of from to 200,000centipoises at a temperature of 20 C. Practical results: are achieved inthe process of the aboveexample when the cysteine 3 ranges, by totalweight of the fluid, from 0.001 to 0.40% of. the fluid.

The present invention may be applied to a variety of 'silver transferprocesses other than the one specifically referred to above. The fluidmay be spread either between the adjacent faces or on one of the remotefaces of the superposed silver halide silver-receptive strata before orafter photoexposure. The fluid itself may contain a silver precipitatingagent in the presence of which print formation occurs, so that thesolidified layer of said fluid contains the desired silver transferimage, in accordance with the principles of Patent No. 2,662,822 issuedto Edwin H. Land on December 15, 1953, e.g., a composition like that ofExample 1 of said patent. In fact,

- the additive of the present invention is especially useful in theprocesses of the latter patent to render more blue.

black the sepia images which are normally obtainedfrom using thecompositions of the aforesaid patent. When used in these compositions,the additive of the present invention is preferably present inproportions varying from 0.002 to 0.60% of the composition by weight. Itmay also be usefully employed in processes which provide a support witha photosensitive coating by application of a photosensitive material inaccordance with the principles of United States Patent No. 2,846,309granted August 5, 1958 to Edwin H. Land. Before photoexposure, such aprocess may initiate development to provide a dynamic photosensitivestratum in which a latent image later formed develops spontaneously inaccordance with the principles of United States application Serial No.498,672, filed April 1, 1955 in the name of Edwin H. Land. The twosheets may be stripped apart to uncover the resulting print or may beretained in superposed relation, when the maximum density of thenegative is small compared to the maximum density of the positive print,in accordance with the teachings of United States Patent No. 2,861,885,granted November 25, 1958 to Edwin H. Land. When the various materialsare associated in the form of a film -unit having a pair of sheets and acontainer whose contents are to be spread between the sheets, thephotographically active materials, including the cysteine, may becarried at a variety of locations, e.g., in the container or on one ofthe sheets. The photosensitive emulsion may be coated over thesilver-receptive stratum, with the processing liquid being applied tothe surface of the emulsion. After the desired transfer has beeneffected, the emulsion layer is stripped off.

The present invention thus is based upon the discovery of the uniqueproperties of cysteine in relation to silver diffusion transferprocesses and compositions useful therein.

This application is a continuation in part of my 00- pendingapplication, Serial No. 619,604, filed October 31, 1956 (now abandoned).

and composition without departing'from the scope of the invention hereininvolved, it is intended that all matter contained in the abovedescription or shown in the accompanying drawing shall be interpreted asillustrative and not in a limiting sense.

What is claimed is:

l. A photographic composition comprising an alkaline aqueous solution ofa silver halide solvent fixer, a silver halide developing agent andcysteine, said cysteine ranging from about 0.001 to 0.60%, saiddeveloper ranging from about 1 to 8% and said silver halide solventfixer ranging from about 0.3 to 10%, by total weight of saidcomposition.

2. The photographic composition of claim 1', wherein said composition isa fluid possessing a viscosity of from 100 to 200,000 centipoises at atemperature of 20 C.

3. The photographic composition of claim 1, wherein said solutionincludes a silver precipitating agent.

4. A photographic process for producing a visible print, said processcomprising the steps of applying a processing liquid to an exposedsilver halide emulsion and efiecting development of said exposed silverhalide by a silver halide developing agent, reacting a silver halidesolvent with at least a portion of the unexposed silver halide to form asoluble silver complex, and transferring said soluble silver complex toa silver-receptive stratum in superposed relationship with said silverhalide emulsion, said silver-receptive stratum containing a silverprecipitating agent whereby said transferred silver complex isprecipitated to form said visible print, said process being efiected inthe presence of cysteine in a concentration, by total weight of saidprocessing liquid, of about 0.001 to 0.60%.

5. The photographic process of claim 4, wherein said silver halidedeveloping agent ranges from about 1 to 8%, and said silver halidesolvent ranges from about 0.3 to 10%, by .total weight of said liquid.

6. The photographic process of claim 5, wherein said liquid contains athickener in sufiicient quantity to impart a viscosity of from 100 to200,000 centipoises at a tem- .perature of 20 C.

7. The photographic process of claim 4, wherein said silverprecipitating agent is contained in said processing liquid, and saidvisible print is contained in a solidified layer of said processingliquid.

References Cited in the file of this patent UNITED STATES PATENTS UrbachSept. 14, 1948 Land Apr. 3, 156

OTHER REFERENCES Chem. Abstracts, 41, 20l6d (1947).

I changes maybemadeinthe abovepm Chem. Abstracts, 33, 2498 (1939).

4. A PHOTOGRAPHIC PROCESS FOR PRODUCING A VISIBLE PRINT, SAID PROCESSCOMPRISING THE STEPS OF APPLYING A PROCESSING LIQUID TO AN EXPOSEDSILVER HALIDE EMULSION AND EFFECTING DEVELOPMENT OF SAID EXPOSED SILVERHALIDE BY A SILVER HALIDE DEVELOPING AGENT, REACTING A SILVER HALIDESOLVENT WITH AT LEAST A PORTION OF THE UNEXPOSED SILVER HALIDE TO FORM ASOLUBLE SILVER COMPLEX, AND TRANSFERRING SAID SOLUBLE SILVER COMPLEX TOA SILVER-RECEPTIVE STRATUM IN SUPERPOSED RELATIONSHIP WITH SAID SILVERHALIDE EMULSION, SAID SILVER-RECEPTIVE STRATUM CONTAINING A SILVERPRECIPITATING AGENT WHEREBY SAID TRANSFERRED SILVER COMPLEX ISPRECIPITATED TO FORM SAID VISIBLE PRINT, SAID PROCESS BEING EFFECTED INTHE PRESENCE OF CYSTEINE IN A CONCENTRATION, BY TOTAL WEIGHT OF SAIDPROCESSING LIQUID, OF ABOUT 0.001 TO 0.60%.